Various types of storage containers are well-known for containing liquids, including agricultural chemicals. Some storage containers include double walls which precludes spillage or leakage of the liquid if the outer wall is damaged, such as a puncture, without damage to the interior wall of the container. If there is a leak in the inner tank, the liquid is captured by the outer tank. Some double walled containers are fabricated as a single unit in which the inner and outer walls cannot be separated. Other double wall containers include separate inner and outer tanks which nest together. However, the structure and manufacture of all these double wall containers is relatively complex, and thus costly.
In designing and manufacturing plastic molded tanks, it is important to maintain the integrity of the tank, including maximum strength and minimal stresses. Molded plastic tanks with continuous, non-interrupted sidewalls have greater strength and less stress points than tanks having depressions or other formations in the sidewall. Such depressions increase the circumferential or hoop stress of the tank sidewall, and thus weaken the sidewall strength. As the level or volume of liquid or particulate material contained in a tank increases or raises, the forces generated by such contents increases. Thus, maintaining maximum sidewall strength and minimizing hoop stress becomes more important along the height of a cylindrical tank. Interruptions in the cylindrical hoop created by depressions in the sidewall may cause the sidewall to bulge, and eventually fail, under the force of the tank contents.
Accordingly, a primary objective of the present invention is the provision of an improved storage container for liquids having separate inner and outer tanks.
Another objective of the present invention is the provision of an improved storage container for liquids which has a double walled construction.
A further objective of the present invention is the provision of an improved storage container for liquids having an inner tank which can be removably nested within an outer tank.
Still another objective of the present invention is the provision of a dual tank assembly having notches in the outer tank to engage, support and align the inner tank when the nested tanks are in a horizontal shipping position.
Another objective of the present invention is the provision of nesting inner and outer tanks wherein the outer tank has lifting eyes for receiving hooks to lift the nested tanks together.
A further objective of the present invention is the provision of an improved double tank assembly wherein the outer tank has short alignment notches adjacent the bottom which substantially maintain the hoop strength of the cylindrical tank sidewall substantially along the height of the sidewall.
Still another objective of the present invention is the provision of a dual tank assembly for storing liquids wherein the sidewall of the outer tank has a cylindrical hoop extending uninterrupted substantially from the top of the tank to the bottom of the tank.
Yet another objective of the present invention is the provision of an improved storage container for liquids wherein an inner tank has a top rim which overhangs an upper shelf or shoulder on the lower tank.
Another objective of the present invention is the provision of an improved storage container having separable nesting inner and outer tanks with means to preclude rotation of the tanks relative to one another when assembled together.
A further objective of the present invention is the provision of an improved storage container for liquids having dual inner and outer tanks which are molded plastic.
Another objective of the present invention is the provision of an improved storage container for liquids wherein an inner tank has a bottom, a sidewall and a top molded as one piece and an outer molded tank having a bottom, a sidewall, and an upper open mouth for receiving the inner tank.
A further objective of the present invention is the provision of an improved storage container for liquids which is economical to manufacture and durable and safe in use.
These and other objectives will become apparent from the following description of the invention.